Avermectins
As avermectins a group of is neurotoxins designated as end products of the fermentation of the "beam fungus" Streptomyces avermitilis arise. In some cases the fermentation products are then chemically treated; this creates so - called semi - synthetic avermectins .
For their discovery, William C. Campbell and Satoshi Ōmura received the 2015 Nobel Prize in Physiology or Medicine .
Chemistry and representatives
Chemically speaking, the avermectins are macrolides ; H. macrocyclic lactones , which include ivermectin , selamectin , doramectin and abamectin .
The following derivatives of avermectin are described:
| Avermectin derivative |
C-22, C-23 bond |
Substituent at C-5 |
Substituent at C-23 |
Substituent on C-25 |
| A 1a | C = C | -OCH 3 | -H | sec -butyl |
| A 1b | C = C | -OCH 3 | -H | iso- propyl |
| A 2a | C-C | -OCH 3 | -OH | sec -butyl |
| A 2b | C-C | -OCH 3 | -OH | iso- propyl |
| B 1a | C = C | -OH | -H | sec -butyl |
| B 1b | C = C | -OH | -H | iso- propyl |
| B 2a | C-C | -OH | -OH | sec -butyl |
| B 2b | C-C | -OH | -OH | iso- propyl |
Application and mode of action
Avermectins are in the control of parasites of domestic and farm animals , and prophylactically in crops from mite infestations and since May 2015 in adult humans against the skin disease rosacea used. They show broad activity against nematodes and mites . Useful doses in animals move in the range of 300 μ g per kg of body weight or less; A 2% aqueous emulsion is used for plant application. Unlike most other macrolides , avermectins have no antibacterial or fungicidal effects.
The avermectin neurotoxins increase in invertebrates the membrane permeability of the nerve or the muscle cells for chloride - ions by binding to glutamate -activated chloride channels. This leads to hyperpolarization of the cell membrane and a blockage of the conduction of excitation and thus paralysis of the parasites. In addition, higher doses of avermectins also influence the receptors for γ-aminobutyric acid (GABA) in synapses , which use GABA as a neurotransmitter . Due to the increased release of GABA, the affected pests are paralyzed and die.
Since GABA is also found in the brain of vertebrates , these active ingredients can trigger side effects and toxic effects that manifest themselves in fatigue. Birds in particular (especially finches and budgies) as well as rats and animals with MDR1 defects are relatively sensitive to avermectins. In most mammals , however, avermectins do not cross the blood-brain barrier , which protects them.
Web links
- Avermectine entry on Vetpharm, accessed August 11, 2012.
Individual evidence
- ↑ K. Hardtke et al. (Ed.): Commentary on the European Pharmacopoeia Ph. Eur. 5.0, Ivermectin. Loose-leaf collection, 19th delivery 2005, Wissenschaftliche Verlagsgesellschaft Stuttgart.
- ↑ Atanas Georgiev Dimitrov (2005): Integrated production of tomatoes ... , p. 42, Tenea Verlag Ltd., ISBN 3865041167 .
- ↑ Ivermectin: An Insecticide Against Rosacea , Pharmazeutische Zeitung, May 12, 2015, accessed January 3, 2016.
- ^ Hotson, IK (1982): The avermectins: A new family of antiparasitic agents. In: JS Afr. Vet. Assoc. Vol. 53, pp. 87-90, PMID 6750121 .
- ↑ a b Campbell, WC et al. (1983): Ivermectin: a potent new antiparasitic agent. In: Science. Vol. 221, pp. 823-828, PMID 6308762 .
- ^ DC Plumb: Veterinary Drug Handbook . PharmaVet Publishing, White Bear Lake (USA) 199, ISBN 0-9626619-0-2 .